The present invention relates to the general field of analyzing fluids. The invention applies more particularly to automatically analyzing fluids, whether biological fluids or otherwise.
In a particular application, the fluid is of human or animal origin. The invention is then particularly applicable to the field of analyzing blood. In this field, it is particularly useful to design systems and methods that perform such analyses in automatic manner.
In known systems and methods for performing hematological analyzes, total blood samples are generally taken directly from a patient, and then mixed with an anticoagulant. The initially-taken blood sample is then contained in a collecting vessel, usually a tube, optionally closed by a stopper. Conventionally these are said to be samples of total or complete blood.
Fluid analysis, in particular hematological analysis, generally requires a plurality of fractions of the total blood sample to be available. This makes it possible to perform a plurality of analyses or measurements on the same initial sample.
In the field of analyzing blood, known blood analyzers enable both different parameters to be measured and various elements constituting blood to be counted in order to obtain information about the state of health of patients. These parameters include in particular red and white corpuscles, hemoglobin, or indeed platelets.
It is then necessary for the initial sample to be divided into a plurality of fractions, referred to as aliquots. These aliquots are mixed with various reagents, and they are subjected to different treatments depending on the analyses that are desired.
Various systems and methods have been developed for taking blood from the collecting tube on one occasion only. This avoids the need to manipulate the tube several times with the attendant risk of contaminating the blood contained in the collecting tube. This also decreases the time the analyzer is occupied and increases the rate at which analyses can be performed, by releasing the collecting tube earlier.
In addition, known systems and methods generally enable the total volume taken on one occasion only to be smaller than would be possible if the blood sample were to be taken on several successive occasions.
Known systems and methods thus aliquot the blood before mixing it with various reagents and distributing it amongst various recovery and/or analysis means. The aliquots prepared with different reagents serve to determine values for the parameters of the sample, e.g. by means of optical measurement systems, thereby obtaining analysis results for all of the elements that constitute the blood.
Known systems and methods for fractioning the blood sample into multiple aliquots generally involve sampling valves that enable different aliquots to be taken on a single occasion and that enable them to be delivered on a plurality of occasions, so as to release the tube as quickly as possible. The aliquots present in the valve are then distributed to the same recovery and/or analysis means, one after another, or to different recovery and/or analysis means, optionally simultaneously.
More particularly, the invention thus relates to the field of sampling valves that enable a fluid to be sampled, in order to perform a plurality of analyses using various reagents.
French patent application FR 2 622 692, in the name of the Applicant, describes a so-called “linear” sampling valve in which a central moving member is sandwiched between two stationary members. It is necessary to rectify the faces of the members that are in friction contact with one another. That means it is necessary for four faces to be rectified in order to fabricate a valve in accordance with that document, so the cost of such a valve is high. In that valve, the movement of the moving portion defines a section in a channel present in the stationary portion connected to the moving portion. This section is subsequently isolated by moving the moving portion, and it corresponds to the volume of the aliquot that is to be used.
Other sampling valves also exist that are of a rotary type in which a member is movable in rotation between two stationary members.
By way of example, one such valve is described in U.S. Pat. No. 4,948,565 filed in the name of Fisher Scientific. Once more, it is necessary for four active faces to be rectified very accurately, thereby leading to high costs. The aliquots taken in a first position are subsequently dispensed to the measurement systems in a second position. Thereafter the entire system is rinsed in a third position. In the second position, it is not possible to separate at least some of the aliquots of blood from the reagents, and contamination may occur by liquid migration, in particular when certain analyses are not performed. The term “contamination” is used herein to mean the beginning of a reaction between an aliquot and a reagent, and also mixing between aliquots of two different samples. This makes it necessary to dispense new reagent to each loop as soon as it is in contact with the fluid for analysis, even if no analysis is to be performed subsequently. This leads to a wastage of reagent that is naturally economically harmful, and that is also often ecologically harmful.
U.S. Pat. No. 6,662,826 in the name of Abbott protects a four-member sampling valve. Fabricating such a valve requires six ceramic faces to be machined in order to achieve good operation, and that is extremely expensive. In addition, that valve does not enable distribution to be performed sequentially towards one or more recovery and/or analysis means. Once more, the blood aliquot is not physically isolated from the reagents and the taken sample may become contaminated.
U.S. Pat. No. 5,390,552, filed by Toa Medical Electronics, describes a valve made up of three members, two of which are stationary and one movable. That valve thus presents the same drawbacks as the valves described above. In addition, that valve does not propose timed delivery to a single measurement appliance.
U.S. Pat. No. 5,255,568, filed by Coulter Corporation, describes a valve having three members, two of which are stationary, and the middle third member is movable. Once more, it is necessary to machine four faces very accurately in order to obtain good results. There is still no possibility of timing the delivery of aliquots. Finally, in that patent, the valve can take only two positions, the first corresponding to sucking in aliquots and to rinsing the loops, and the second corresponding to dispensing reagents. Once more, the aliquots of blood and the reagents cannot be separated physically, and contamination may occur with migration taking place between the blood and the reagents.
All of those valves also present the drawback of limited access to the inside of the parts in order to clean them. When the orifices need to be purged, disassembly is not easy. Furthermore, when reassembling the valve, it is necessary to ensure that movements between the movable and stationary parts are very accurately adjusted. The large number of members constituting those valves thus constitutes a drawback.